Xamarin Forms: How to use UIViewPropertyAnimator in Xamarin.iOS - xamarin

Question

I want to use UIViewPropertyAnimator in Xamarin.iOS, but my project is actually part of Xamarin Forms. I created a dependency service and tried the following:
var renderer = Platform.GetRenderer(view);
var uiCubicTimingParameters = new UICubicTimingParameters(new CGPoint(x: 0.4, y: 0), new CGPoint(x: 0.2, y: 1));
var uiViewPropertyAnimator = new UIViewPropertyAnimator(duration, uiCubicTimingParameters);
uiViewPropertyAnimator.AddAnimations(() =>
{
renderer.NativeView.Transform = CGAffineTransform.MakeTranslation(300, 0);
});
uiViewPropertyAnimator.StartAnimation();
The problem with this approach is that it's directly updating the native view, but Xamarin Forms view is no longer in sync. I noticed some weird UI issues because of this.
What's the right way to use UIViewPropertyAnimator in the case of Xamarin Forms?

Answer 1

Before starting the animation , first set its initial Transform , and don't forget to notify Forms of the final change when animation complete .
Refer to the following code
public async Task TranslateViewAsync(View view)
{
var finished = false;
CoreFoundation.DispatchQueue.MainQueue.DispatchAsync(() =>
{
var renderer = Platform.GetRenderer(view);
renderer.NativeView.Transform = CGAffineTransform.MakeTranslation(375, 0);
var uiViewPropertyAnimator = new UIViewPropertyAnimator(0.3, UIViewAnimationCurve.EaseOut, () =>
{
renderer.NativeView.Transform = CGAffineTransform.MakeTranslation(0, 0);
});
uiViewPropertyAnimator.AddCompletion(p =>
{
finished = true;
});
uiViewPropertyAnimator.StartAnimation();
});
while (!finished)
await Task.Delay(10);
}
Refer to https://github.com/xamarin/Xamarin.Forms/issues/6999#issuecomment-542488010 .